In engines of the well known four-stroke cycle piston type the engine pistons have the dual function of pumping the charging air into and out of the engine cylinders as well as providing the required functions of compressing the charge and expanding the burned gases to produce power. There are, however, other forms of internal combustion engines wherein the pistons or other expansible chamber elements, are utilized solely to compress and expand the working gases and supplemental means are provided to charge and scavenge the cylinders. Common examples are piston type two-stroke cycle internal combustion engines which are usually provided with some form of charging air blower, commonly driven directly by the engine.
Two-stroke cycle engines may be turbocharged and provided with aftercooling means for cooling the inlet charge after compression. This is especially common with diesel engines. Usually the turbocharging arrangements for such engines provide adequate energy to supply the full air charge required for operation at the higher load end of the engine operating range. However, some supplemental means for providing charging air for starting and low load operation may be required. Such means may take the form of mechanical or other devices for supplementing the turbocharger drive when the exhaust energy is not sufficient, or it may involve the use of a separate, usually positively driven, blower connected in series with the turbocharger compressor so as to supply adequate induction air to the engine under all operating conditions where the exhaust energy is not sufficient to provide the required charge.
One form of aftercooled, turbocharged two-cycle diesel engine having an engine driven supplemental charging blower in series with the turbocharger is shown in U.S. Pat. No. 4,028,892 Hinkle, granted June 14, 1977 to the assignee of the present invention. Many other exemplary arrangements of turbocharged internal combustion engines having positively driven blower means for supplemental air charging are also known in the prior art.